Unfortunately neither overflow: auto, or scroll, produces scrollbars on the iOS devices, apparently due to the screen-width that would be taken up such useful mechanisms.

Instead, as you've found, users are required to perform the two-finger swipe in order to scroll the overflow-ed content. The only reference, since I'm unable to find the manual for the phone itself, I could find is here: tuaw.com: iPhone 101: Two-fingered scrolling.

The only work-around I can think of for this, is if you could possibly use some JavaScript, and maybe jQTouch, to create your own scroll-bars for overflow elements. Alternatively you could use @media queries to remove the overflow and show the content in full, as an iPhone user this gets my vote, if only for the sheer simplicity. For example:

Sadly not, all variations of css that might apply scroll-bars to page elements are, unfortunately, verboten. The only options are: 1, use JavaScript to emulate (what should be a native function) or, preferably, 2, use the @media queries to create mobile-specific stylesheets that obviate the need for scrolling-elements.
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David ThomasOct 2 '10 at 12:41

11

starting with ios 5beta a new property -webkit-overflow-scrolling:touch can be added which should result in the expected behaviour.
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kritzikratziJul 13 '11 at 13:41